1. Field of the Invention
The invention relates to devices used for flaw detection of long-distance pipelines, mainly oil and gas pipelines through non-destructive methods by passing inside the pipeline an intelligent scraper with monitoring sensors mounted thereon and responding to any diagnostic parameter of the pipeline. The invention primarily relates to means for attaching sensors and maintenance of their necessary spatial location with respect to the pipeline surface during the travel of the scraper.
2. Description of the Related Art
Known in the art are sensor carriers (see GB939172, U.S. Pat. Nos. 3,496,457, 3,449,662, 3,810,384, 3,835,374, 3,940,689, 3,949,292, 3,967,194, 3,973,441, GB2020023, U.S. Pat. Nos. 4,342,225, 4,457,073, 1,157,443, 4,717,875, 4,598,250, DE3506622, DE3706660, U.S. Pat. No. 4,910,877, 4,945,306, 4,953,412, 5,115,196, 3,755,908, 5,460,046, DE19747551, DE3719492) for an in-tube scraper with sites for sensors which are arranged on a surface with axial symmetry (inscribed into a surface with axial symmetry). The carriers are characterized in that they include housing and sensor supports. The use of the above devices does not allow one to obtain a resolution sufficient for identification of defects such as pinpoint corrosion or cracks in the pipeline wall.
Also known in the art are sensor carriers (see U.S. Pat. Nos. 3,529,236, 3,543,144, 3,786,684, RU2139469, RU2139468) for an in-tube inspection scraper with setting places for sensors which are arranged on a surface with axial symmetry (inscribed into a surface with axial symmetry). The carrier is characterized in that it includes a housing and one or several belts of sensor supports spring-loaded in the radial directions and secured on the housing with the help of pivot joints. Each support has setting places for sensors. The advantage of such a sensor carrier is that it allows one to scan the whole surface of the pipeline with overlapping the zones monitored by individual sensors. The main disadvantage of such a carrier is that when it passes a pipeline section with a defect of geometry, for example, a dent, the sensor supports behave as rigid elements, and a knock of the front part of the support against a dent (projection on the pipeline internal surface) is accompanied by a departure of whole support from the non-deformed part of the pipeline. An increase of the distance between the sensors and the internal surface of the pipeline imparts the efficiency of the sensors, and such sections of the pipeline with defect of geometry remain to be not inspected.
Known in the art is a sensor carrier (see U.S. Pat. No. 4,098,126) for an in-tube inspection scraper with setting places for sensors, which are provided on a surface with axial symmetry. The carrier is characterized in that it includes an elastic sleeve whose diameter is less than the pipeline bore diameter, the sensors are installed along the periphery of the sleeve and said sensors are inscribed in a cylinder whose diameter exceeds the sleeve diameter. Such a carrier is advantageous in that, when the scraper travels along a pipeline section with an insignificant defect of geometry, like a dent, the sensors adjoin the deformed surface of the pipeline. The basic disadvantage of such a carrier is that the carrier sensors are arranged as a single belt, and since some distance separates the sensors from each other, this distance restricts the linear resolution of the inspection scraper with such a carrier. Furthermore, the distance between the adjacent sensors cannot be less than the sensor size/and this also restricts the linear resolution. Besides, when the carrier passes pipeline sections having major defects of the geometry in the cross section, the sensors move away from the non-deformed part of the pipeline near the defect of geometry and this is followed by a collapse of the sleeve with sensors. When testing the pipeline consisting of pipes having essentially different thickness of the pipe walls, for example, in the presence of earlier repaired pipeline sections, on the sections with an increased wall thickness, as well as in the presence of a fixed foreign object on the internal pipe surface, the movement of the sensor carrier can be accompanied by a collapse of the sleeve and a loss of orientation of some sensors. Besides, installation of the sensors outside results in a damage of the sensors by such obstacles as jar washers.
A related device for the claimed group of inventions is a known sensor carrier (see U.S. Pat. Nos. 4,807,484 and its equivalents CA1307129, DE3626646, EP0255619, ES2026869, NO172956, NO873252) for an in-tube inspection scraper with setting places for sensors which are arranged on a surface with axial symmetry. The carrier is made as an elastic cylindrical sleeve with protuberances forming a cylinder whose diameter is larger than the internal diameter of the pipe; the sensors are located in the depressions of the sleeve, the protuberances and depressions being oriented under an acute angle to the sleeve axis.
This carrier is advantageous in that the sensors installed along the lines oriented at an angle to the carrier axis allow one to scan the entire surface of the pipeline with overlapping of the zones monitored by individual sensors; the installation of the sensors in the sleeve depressions protects them against damage on such obstacles as jar washers; when passing the pipeline section with a defect of geometry such as a dent, the sensors adjoin the deformed and non-deformed surfaces of the pipeline both along the axis and along the perimeter of the pipeline.
The disadvantage of such a carrier is that the elastic sleeve carrying a large number of sensors with associated cables (which provide high linear resolution) or utilization of heavy sensors (for example, magnetic) with long length and low thickness of the sleeve and, respectively, good elasticity, results in deformation of the elastic sleeve under the total weight of the sensors and cables. This leads to a formation of a gap between the sensors at the top part of the elastic sleeve and the internal surface of the pipeline, in which case the presence of a gap interferes with uniform pressure of the sleeve to the internal wall of the pipe when filling the starting chamber with fluid to be conveyed. The increase of the sleeve rigidity (to avoid the above phenomenon) is accompanied by a loss of elasticity of the sleeve when enveloping the defects of geometry of the pipeline and formation of gaps between the sensors and the internal surface of the pipeline near the defect.
Besides, the gaps between the sensors and the internal surface of the pipeline are also formed when enveloping the defects of geometry by the sensors arranged at the front wall of the sleeve whose ability of compressing in the plane passing through an carrier axis is much lower than at the section of the sleeve remote from its front wall.